In the field of electronic devices, advances have been made in the development of thin, large-area electronic devices. For example, in flat panel displays using organic EL devices, it is common to use a structure wherein the organic EL devices are disposed between two substrates of an inorganic material such as glass. By bonding these two substrates closely together at their peripheral portions by using so-called frit materials, the organic EL devices can be sealed from the external environment and thereby protected from oxygen and moisture which may have detrimental effects.
In recent years, there have been demands to make thin, large-area electronic devices more flexible. In order to respond to these demands, the use of polymer films such as polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) as substrates for devices has been suggested.
However, the above-mentioned frit materials require laser irradiation for bonding, and are therefore not suited for use in sealing materials for polymer films with a low melting point. Furthermore, frit materials are deficient in elasticity and are not suitable for electronic devices such as flexible displays.
On the other hand, techniques using organic adhesives have been developed in order to bond and laminate polymer films at a low temperature (Patent Document 1). However, it is difficult to finely pattern an applied organic adhesive for mounting electronic devices, so bonding methods using organic adhesives are not suitable for mounting of electronic devices for which the structures of the bonding interface are becoming smaller and smaller. Furthermore, in special environments such as in a vacuum, organic solvents will be released by evaporation or the like from the layers of adhesive in the final product over time, which can result in reduced mechanical strength of the bonded portions.
Additionally, organic materials are used as adhesives not only for bonding polymer films, but also, for example, in the touch panels of smartphones and the like in which a polymer film is bonded to a glass substrate. However, with organic adhesives, the probability of defects such as bubbles occurring rises as panels become larger, and this reduces yield, which is a factor in raising final costs.